Rectification of alternating current



g- 1932- R. H. WILLIAMSON 1,874,840

RECTIFIGATION OF ALTERNATING CURRENT Filed Aug. 21, 1929 Z8 If I v Invent-01M Raymond H.Willia-mson,

HisAttorne control? Patented Aug. 30, 1932 ci irtsiorotlir ere la n 3 v i, .i

;ib iei mr ',a t a 'ied c areetypeht e 1,. larly' suitable for of eratien e infe e their 1 'zdp v' rgivl ar le h nd? i rer'etmg'vbl eg" i t di co inue ous control elec ric-raj s; er valves P o no e. {a rem te-,1 w

I anrfin jwliicfithe starting of zscu rrenjt "the" valve de i'rninedby' the potentialo'n its control 'gri'dfbnt in which the current in the valve-can be' int'err'upted' only by' "r educing; its] anode potential below' the criticali'value',gwhi'ch may he of the order of 3o15or volts. It has been-found thatva'lves ofthis'type are usually. incapable of limiting the current whicl'i they transmitto a valuewhich preventsinjiiry or destruction of the 4 valves themselves-or the load devices which are energized nan: the circuit iii which: they an improved apparatus" including" discontinuous con't'ro'lelectric valves" for transmittingenergy Bet-ween direct and alternating circuits in Whichthe current-through the valves will be interrupted upon the" occur-- rence ofpnedeterminedabnormali conditions.

7; Iti's:-a furtherobj'ect of myinvention to provide an: improved apparatus includingelectriowvalvesrfor transmitting energy be tweendirectiandelternatingcircuitsin which the-currentthmughthev valves-will beina terrupteduponathe occurrence of: a predetermined current in the direct current circuit PATENT OFFICE assmnon '10 GENERAL ELECTRIC :commm; a ooma onanon or new YORK nncirrrrcnmion or AnTEIiNA-mnie cnnnnn'r which thisinterru'ption will be maintai'n'edg for a predetermined interval.

In accordance with my invention the occnrr nce of destructive current in the electric valves is prevented by an improved arrangixiafit whereby a negative voltage is applied .t'ov the control grids of electric valves iel dadicurrent vhas reached a predcte minedfvalne a-nd' whereby the anode voltagejis' centi'ollediin such a way as to inslire that-the anode current is interrupted by th'e'n grid whenit is subjected to this-negative lily invention will he hetter understood I from the following description when considf ered in connection with the accompanying drawingg aiid its scope will he pointed out I in the appended claims.

e .drawing isa circuit diagram of a rectifyingsystem wherein my invention has been emhodiedi' i This system includes alternating current supply terminals IO and direct current terminails 11- hetweenwhich electrical power is transmitted through a transformer 12, a plurality of'discontinuous control electric valves 13,14,15 16, 1 7 and 18, a smoothing reactor 19,,a resistor 20 and a resistor 21. It will be observed that the valve 13 is connected to the load circuit in series with the valve 16, that the valve 14' is likewise connected in series with the valve 17 and that the valve 15 is similarly connected with the valve 1-8. The directcurrent-load is indicated at 22 which is intendedftorepresent' any device which utilizes. direct a current" in its operation. A smoothingicondenser 29 is connected in shunt to the loadicircuit and the resistor 21.

The electric-valves 13 to 18 inclusive are each provided with an anode and a cathode and} are preferably of the discontinuous control type, The valves113, Hand 15 are each provided withagridwhich is-connected to its cathodethrough: the bias resistor 21 and avol'tage:responsive-device 23 which may be a glow tube or other device-operable to apply grids is a condenser 24 and an impedance element or grid leak 25.

During the operation of the system the direct current load may be increased or short circuited. In either case when the potential drop across the grid bias resistor 21 exceeds the break down voltage of the device 23,the valves 13, 14 and 15 are biased to cut oil and the direct current is interrupted. In the absence of the grid leak resistance 2 5,the' cur rent would be interruptedindefinitely;- The function of this resistor is to allow the char e to leak oil the condenserandto permit 't e current to be reestablished. When this occurs current will be supplied to the direct current circuit forone-third of a cycle and will again be interrupted if the direct currentload" is still short circuitedQ If the'short circuit or overload has been removed by the time the charge leaks over the condenser 24; the 'normal operatin condition will be resum'ed,

The use oi the smoothing reactor 19 in; volves an additional complica'ti'on in the pro; tection of the rectifier and'the direct ci' rrent load. As previously indicatedthevalvesglig to 15 are of a type in which the of preventing the starting of. current between 'f the cathode and anode, but is incapable'of in 'fl terrupting the current after it has been started. I

When the rectifier is overloaded or the (h rect current circuit is short circuite'd, a very" high rate of change in the current of the smoothing reactor 19 occurs. Thisfpr'oduces a comparatively high voltage-betwe enthe terminals of this reactor, and this voltage "is added to the anode voltage of the particular valve which happens to betr'ansmitting current at that instant. This reactor voltage will, if it is large enough, hold a potential which is always positive on-the anode circuit of the valve and which will prevent the anode current from reaching zero. If this'occurs, the grid is ineffective to produce cut-oil and he current is not interrupted. It is therefore, necessary to provide some means where by the induced voltage ofthe smoothing reactor 19 may be controlled when the current changes suddenly. i This result is produced by including a valve 26 which is similar in its operation to the valves 13 to 15, and which is arranged 'to have potential applied to its grid through the resistor 20 and a bias rectifier 27. With this arrangement the valve 26 transmits no current during the normal operation of the ystem. When the direct current loaddiecomes abnormal however, the negative voltage applied to the grid of the valve 26 through 2 the bias rectifier 27 is neutralized by-the op posed voltage produced in the resistor 20, and

the load current is shunted through the valve 26, thus permitting the anode current of the valves 13, 14 and 15 to be interrupted by the- 1 grids of these valves. 1

It will be readily understood by those skilled in the art that current is transmitted from the secondary windingv28 of the transformer 12 to the direct current load circuit successively through the valves 13, 14 and 15, and is returned from the lo ad circuit to the secondary winding of the transformerg l2 successively through the valves 16, 17 and 18. The improved rectifying system has the adz-vantages that the current is filtered andzmain-sz tained-snbstantiallyzconstant by means of the smoothing reactor 19 and the smoothing condenser 29 which is-connected in shunt to the direct current load circuit, and that int-erruption of the-c'urrent' by the grids of the valves v 13 14 and 15 insured .under, all conditions of operation regardlessfot the voltage produced at;jthe terniinals (itthe smoothing I re ctor when the magnitude of the direct current, is sud my changed. I

as? i ei eppe fienmhe "wave; 26: are grid control circuit may be replacedlbya low ere tube or otherfvcl fi ge responsive deyicew theload cu riieiil t s'u e S O s jhiel'di IL'W fe Y JQl by Letters e a mell- Be lin ate ed between 'sai'd terminals and provided with a sr lf 'ce t i ie wer tr m t between its cathode and'ariode, means re'sponsive to ,thecurrent e f-said direct-current te'r- I minals for producing'a negative bias voltage;

and a; Voltage responsive device'operable to apply saidneg'ativeibias voltage said grids when it exceeds a predetermined value.

Q2. The combinationof alternating and di- 1 current transmitted between its cathode and anode, means connected lnseries with said direct current terminals for producing a neg ative biasvbltage, and a voltage responsive.

device operable toapply saidvoltage to said grid when the current of said direct current circuit exceeds a predetermined value.

3. The combination of alternating and direct current, circuits, means connected between said circuits includinga reactor and a disconti1 1uous control electric valve of the vapor electric type provided with a grid for controlling, the current transmitted between. its cathode andanode; means connected in series with said direct current terminals for producing a negative bias voltage, 'a voltage responsive device operable to apply said-voltage to said grid when the load c'urrent 'of- ,aiidfde i'rete seam: Q thQ l sd" i T 1 Thel qmbil flfiion of alterriating and idi-i Q rect" current ter'rni'nale means including a discontinuousfcontrol electric valve connect:

said direct'c'urrent'circuit ex'ceedsa prede-' termined value, and means connected in shunt to'said reactor and arranged tobypasssaid load current when it changes in magnitude at a predetermined rate.

4. The combination of alternating and direct current circuits, means connected between said circuits including a reactor and a discontinuous control electric valve of the vapor electric type provided with a grid for controlling the current transmitted between its cathode and anode, means connected in series with said direct current terminals for producing a negative bias voltage, a voltage responsive device operable to apply said voltage to said grid when the current of said direct current circuit exceeds a predetermined value, and means including an asymmetric conductor connected in shunt to said reactor and arranged to bypass said load current when it changes at a predetermined rate.

5. The combination of alternating and direct current circuits, means connected between said circuits including a discontinuous control electric valve provided with a grid arranged to control the current between its cathode and anode, means for applying to said grid a negative bias voltage dependent on the magnitude of the current of said direct current circuit, a smoothing reactor connected in series with said direct current circuit, and a discontinuous control electric valve connected in shunt to said reactor and operable to transmit the load of said direct current when the potential drop between the terminals of said reactor exceeds a predetermined value.

6. The combination of alternating and direct current circuits, means connected between said circuits including a discontinuous control electric valve provided with a grid arranged to control the current between its cathode and anode, means for applyin to said grid a negative bias voltage dependent on the magnitude of the current of said direct current circuit, a smoothing reactor connected in series with said direct current circuit, a

. discontinuous control electric valve connected in shunt to said reactor and operable to transmit the load of said direct current when the potential drop between the terminals of said reactor exceeds a predetermined value and a second discontinuous control electric valve connected in series with said first mentioned valve.

7 The combination of alternating and direct current circuits, means connected between said circuits including a discontinuous control electric valve provided with a control grid, means responsive to the current of said direct current circuit for producing a negative bias voltage, means operable to apply said negative bias voltage to said grid when it exceeds a predetermined value and means associated with said last mentioned means for dissipating said negative bias only after a predetermined interval.

8. The combination of alternating and direct current circuits, means connected between said circuits including a discontinuous control electric valve provided with a con-' trol grid, a resistor in said direct current circuit for producing a negative bias voltage in accordance with the current flowing therein, voltage responsive means for connecting said negative bias voltage between the cathode and grid of said valve to render said valve non-conducting, and a second circuit interconnecting said cathode and grid including a condenser shunted by a resistor to restore the conductivity of said valve after a predetermined interval.

In witness whereof, I have hereunto set my hand this 20th day of August, 1929.

RAYMOND H. WILLIAMSON. 

